1. Field of the Invention
This invention relates to a control system for an automatic transmission having four main forward speeds and one reverse speed, and equipped with a hydrokinetic torque converter provided with a torsional vibration damper intended to filter the irregularities of engine torque at the speeds for which the converter does not intervene in the transmission of the engine torque.
2. Discussion of Background
Automatic transmissions of this type for motor vehicles are already known which mainly comprise a hydrokinetic torque converter with an integrated torsional-vibration damper, and a planetary gear train transmission, as well as a set of hydraulic, and optionally electronic, control devices that, for control of the various elements of the transmission, take into account the data on the operation of the vehicle, such as particularly but in a nonlimiting way, its speed and load of the engine or the position of the accelerator pedal.
Association of a torque converter and a planetary gear train makes it possible to obtain a continuous variation of the torque applied to the wheels of the vehicle during starts, and on the lower speeds using the torque converter. Moreover, shifts can be made quickly under torque and are damped by the hydrokinetic torque converter and its torsion damper, giving the transmission a great flexibility in operation.
The planetary gear train is controlled by a certain number of hydraulic receivers: in the case of a transmission with four main forward speeds and one reverse, it is possible to use three clutches and two hydraulic-actuated brakes. Shifting is performed sequentially by applying or releasing one of these receivers and releasing or applying the other receiver.